Error on `pacman -Sy` (or `sudo pacman -Syu`, `yay -Syu`):

error: failed retrieving file 'community.db' from xxx : The requested URL returned error: 404
error: failed retrieving file 'community.db' from yyy : The requested URL returned error: 404
...

Remove the following lines from `/etc/pacman.conf`

[community]
SigLevel = PackageRequired
Include = /etc/pacman.d/mirrorlist

ref. https://archlinux.org/news/cleaning-up-old-repositories/